Mpls Terminology; Overview: How Vsi Works; Virtual Switch Interfaces And Qbins - Cisco BPX 8620 Installation And Configuration Manual

Chapter 23 Configuring BXM Virtual Switch Interface
Using MPLS techniques, it is possible to set up explicit routes for data flows that are constrained by path,
resource availability, and requested Quality of Service (QoS). MPLS also facilitates highly scalable
Virtual Private Networks.
MPLS assigns labels to IP flows, placing them in the IP frames. The frames can then be transported
across packet or cell-based networks and switched on the labels rather than being routed using IP address
look-up.
A routing protocol such as OSPF, uses the Label Distribution Protocol (LDP) to set up MPLS virtual
connections (VCs) on the switch.

MPLS Terminology

MPLS is a standardized version of Cisco's original Tag Switching proposal. MPLS and Tag Switching
are identical in principle and nearly so in operation. MPLS terminology has replaced obsolete Tag
Switching terminology.
An exception to the terminology is Tag Distribution Protocol (TDP). TDP and the MPLS Label
Distribution Protocol (LDP) are nearly identical, but use different message formats and procedures. TDP
is used in this design guide only when it is important to distinguish TDP from LDP. Otherwise, any
reference to LDP in this design guide also applies to TDP.

Overview: How VSI Works

This section provides detailed reference to virtual interfaces, service templates, and Qbins.
For information on configuring SES PNNI controllers to work with BPX switches, refer to the Cisco SES
PNNI Controller Software Configuration Guide.
For information on configuring MPLS controllers to work with BPX switches, refer to the Cisco MPLS
Controller Software Configuration Guide.
For details about the commands mentioned here for both PNNI and MPLS controllers, refer to Cisco
WAN Switching Command Reference. Refer to Release Notes for supported features.

Virtual Switch Interfaces and Qbins

The BXM supports 31 Virtual Switch Interfaces that provide a number of resources including Qbin
buffering capability. One Virtual Switch Interface is assigned to each logical trunk (physical or virtual)
when the trunk is enabled (see Figure 23-1).
Each virtual switch interface has 16 Qbins assigned to it. Qbins 0 to 9 are used for Automatic Routing
Management. Qbins 10 through 15 are available for use by a Virtual Switch Interface. (In Release 9.1,
only Qbin 10 was used.) The Qbins 10 through 15 support Class of Service (CoS) templates on the BPX.
You may enable a Virtual Switch Interface on a port, trunk, or virtual trunk. The Virtual Switch Interface
is assigned the resources of the associated virtual interface.
With virtual trunking, a physical trunk can comprise a number of logical trunks called virtual trunks.
Each of these virtual trunks (equivalent to a virtual interface) is assigned the resources of one of the 31
Virtual Switch Interfaces on a BXM (see Figure 23-1).
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
Cisco BPX 8600 Series Installation and Configuration
Overview: How VSI Works
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